The results of the present study suggest that the antidepressant efficacy of duloxetine in individuals with MDD may be attributed, at least in part, to its anti-inflammatory properties, particularly in relation to the peripheral levels of IL-8, IL-12, and IFN-γ, but not IL-1β, IL-2, IL-6, and TNF-α. This evidence concerns the gene IL1B and major depressive disorder.